Help with ECM blower. Solved. Plus how Goodman 9 speed works

[gagecalman]

I had a new Goodman gas furnace and ac installed a few months ago. Everything is running fine but I have a question about the ECM blower. I believe it's a 9 speed constant torque ECM .
I've never has a system with one of these. Only PSC motors.
The speed for the heat and ac are set to the same speed so it has 0.5 TESP.
I notice when it's running the blower will get quiet for a few seconds (maybe slowing down?) and then return to normal. Might happen every 5-10 minutes. There is nothing changing as far as the ductwork.
The condenser power is off (still cool here) but if I set the thermostat to ac the blower does it more frequent.
Is this normal? If it is why?
Thanks!

 

[fitter30]

Model of furnace and first four numbers of serial ( tells month week and year)

 

[gagecalman]

GR9S960603BNAA, S/N 2510.

 

[fitter30]

Tried to find a service manual couldn't. Here's a install. Page34 left side . Writes about high/ low heating which doesn't make any sense? There's only W for heat. Two checks to make with probe style thermometer is temperature rise and when the blower quiets down and burners on should rise. And when thermostat satisfies the shut off temperature wanting the shut off 80-85° to get the most heat out of the furnace. It's adjustable has to be on the main board from 60- 180 seconds. Blower speed changing might show up on the main board read out. Bypass blower door switch. To watch the board.

https://documents.alpinehomeair.com/product/gr9s96gd9s96installmanual%5FCFEDF858%2D6746%2D4846%2DAB20%2DFA713A2229CD.pdf

 

[mm08822]

Does that unit use the blue-tooth app - "CoolCloudHVAC"? It connects to Goodman and Amana furnace control boards.

 

[gagecalman]

Does that unit use the blue-tooth app - "CoolCloudHVAC"? It connects to Goodman and Amana furnace control boards.

I can't find any evidence that it does.

I just thought it might be common with the ECM blowers to do this.

 

[mm08822]

Download the service manual. It has 88 pages of operational details.

I didn't see any mention of the app within it.

 

[txvwnut]

If its doing what I think it may doing its controlling humidity and just keeping the air circulated. My Lennox does that and when I first noticed it I looked and the thermostat(the size of an iPad mini) and it said circulating and then one of the other times it said controlling humidity. The compressor may or may not run at when this is happening.

 

[gagecalman]

Thanks for the reply. My system doesn't have any controls for humidity.

 

[Codyboy]

I have a Goodman gas furnace and at times it runs slow and other times it will ramp up.
No idea why unless it senses it needs more or less heat / AC or airflow to satisfy.

 

[danski0224]

I notice when it's running the blower will get quiet for a few seconds (maybe slowing down?) and then return to normal. Might happen every 5-10 minutes. There is nothing changing as far as the ductwork.
The condenser power is off (still cool here) but if I set the thermostat to ac the blower does it more frequent.
Is this normal?

This does not sound normal.

My guess is that the motor is turning off on thermal limit or there is some other electrical issue.

 

[gagecalman]

This does not sound normal.

My guess is that the motor is turning off on thermal limit or there is some other electrical issue.

I have the fan (G) set to the same speed as the heat and ac. TESP is 0.5 so my blower is about 950 CFM.
When I set the thermostat to "fan on" the blower runs fine with no issues.
It's definitely worse In ac with the condenser off.

 

[danski0224]

I have the fan (G) set to the same speed as the heat and ac. TESP is 0.5 so my blower is about 950 CFM.
When I set the thermostat to "fan on" the blower runs fine with no issues.
It's definitely worse In ac with the condenser off.

Bypass the thermostat and jumper out "fan", "heat" and "ac" and see if the fan motor acts up.

Turn off the AC circuit breaker or disconnect so the condenser doesn't run.

 

[gagecalman]

Condenser disconnected.
Jumped and still same.

Please correct me if I'm wrong but it looks like the way Goodman sets the speeds is they apply different voltages to T1 through T5 terminals. Some speeds have voltage on one or more of them.

I set the ac speed to the lowest setting. Voltage is on T1 only.
I ran it on AC and hooked an analog meter to T1. I also monitored the voltage on Y.

Several times I lost the voltage on T1 and the blower stopped for a few seconds but the voltage came back on. Never lost the voltage on Y.
Definitely worse on the slowest speed. Not quite sure how the ECM works so I'm wondering if it's a board issue.

Thanks for the replies!

 

[Wrench97]

If I remember correctly isn't a jumper tool techs have to bypass the ecm part of the blower? Used to diag if the ECM or the motor is bad.

 

[gagecalman]

I think the Goodman 9 speeds are different.
Think it's a board issue.

 

[BurtEggley]

I'd call Goodman tech support and discuss it with them. That said, you might ask if there are any settings that can cause that. My Carrier knows how long it has been on, and increases speeds and conditioning anytime the initial conditioning is inadequate. If the temperature spread is wide enough then it comes on faster to begin with. The manual on setting one up is quite complex with all the options. You might ask the installer if there are any settings that can change its behavior. If you are the installer then maybe go over the manual again. Just a suggestion what I might do.

 

[gagecalman]

Thanks for the reply.
I did call and was told the board is bad and needs to be replaced. The guy that installed it is coming out to replace it.

In case anyone is wondering how the Goodman 9 speed ECM works here it is.
This is the typical ECM but instead of being programed for a specific speed when voltage is sent to one of the T1 through T5 terminals (5 speeds) the board can send voltage to T1 and T2, T1 and T3, T1 and T4 or T1 and T5 for 4 additional speeds.
The motor is looking for voltage between 6 and 17 VDC. Some motors require 24VAC but not this one.
The settings are in the manual.

 

[danski0224]

Woo hoo.

An update.

 

[gagecalman]

Yea it's always nice to see how things turn out.

 

[BurtEggley]

awesome! Better to get on the other side of it than wonder what is going on. Example - we have a nice mixer that always was bizzare when starting. Sometimes it would start and sometimes not. It has a built in delay to prevent sending flour all over the kitchen if going into high speed quickly, so we thought maybe we didn't understand how to turn it on - the delay, the speeds etc.. January 2026 I replaced the power board and regreased the gears - thinking that maybe it was the board at fault and not us. The new board changed everything - now it works like we always thought it should. So - new electronics can always work goofy out of the box in ways that are hard to anaylze as a fault. Glad you got it worked out. Let us know how it is after the board is replaced.